Aug. 25, 2011 -- Nearly two decades of research on vaccine safety has found that serious side effects are rare and that vaccines do not cause autism, diabetes, asthma, or Bell's palsy.

Although fears about vaccine safety are common, the new study from the nonprofit Institute of Medicine finds that vaccines cause few health problems.

"The findings should be reassuring to parents that few health problems are clearly connected to immunizations, and these effects occur relatively rarely," says Ellen Wright Clayton, MD, JD, director of the Center for Biomedical Ethics and Society at Vanderbilt University. "And repeated study has made clear that some health problems are not caused by vaccines."

"The flu vaccine does not aggravate asthma, and the flu vaccine doesn't cause Bell's palsy," she says. Bell's palsy is a disorder of a nerve controlling facial muscles on one side of the face.

The Institute of Medicine panel looked at more than 1,000 research articles for the study. It was done at the request of the federal Vaccine Injury Compensation Program (VICP). The findings will provide a scientific basis when the VICP, administered by the U.S. Department of Health and Human Services, reviews legal claims about vaccine injuries and decides whether to compensate people who file those claims.

Vaccine Side Effects: Report Details

The committee reviewed the medical literature to see if there was any evidence that the vaccines were associated with 14 different health outcomes. These outcomes include seizures, inflammation of the brain, fainting, and other problems.

For each health outcome, the experts looked at scientific studies and other evidence. They decided how strong the evidence was and whether it pointed to a cause-effect relationship.

For instance, the experts considered 22 studies that looked at the risk of autism after MMR vaccine but found no evidence of a link between the two.

The panel did find some links between vaccines and serious side effects.

"Several vaccines do cause anaphylaxis," Clayton says. Anaphylaxis is a life-threatening reaction that can occur within seconds or minutes after exposure to the allergen.

When these vaccines are given, it's common practice to instruct the patient to wait in the office for a few minutes, Clayton tells WebMD. Typically, the anaphylaxis reaction occurs quickly, she says, and treatment can be given.

Clayton says another possible serious side effect of the MMR vaccine is a type of seizure called a febrile seizure, triggered by fevers. "That's been known for two decades. As a mother and a pediatrician, it's scary."

However, she says, there are almost never long-term consequences of febrile seizures.

Children with compromised immune systems, such as those receiving chemotherapy for cancer, can suffer a variety of side effects from vaccines, Clayton says.

Vaccine Safety: Perspectives

The report has some inconsistencies, says Lyn Redwood, RN, vice president of the Coalition for SafeMinds. The organization is devoted to eradicating autism and other health problems it believes to be caused by mercury and other toxins.

"To me, it is inconsistent that the report says while we acknowledge an association between seizure and inflammation and certain vaccines, we don't acknowledge an association between vaccines and autism," she says.

She cites research that finds children and adults with autism or autism spectrum disorder may have an ongoing brain inflammation. "An all-out effort is needed to better understand why some children are harmed by vaccines and what can be done to make them safer," she says.

"It is equally unacceptable for a child to be harmed by a vaccine-preventable disease as it is for a child to be harmed by a vaccine," she says.

Neal Halsey, MD, director of the Institute for Vaccine Safety at Johns Hopkins University Bloomberg School of Public Health, served as an independent reviewer of the report but did not make recommendations or conclusions.

"Overall, I think it's an excellent report and it helps answer many of the safety questions," he tells WebMD. "I think it's a fair and honest and fairly complete report."

For parents, he says, "I think the important news is that vaccines are generally very safe and that many of the claims about vaccines having caused things like diabetes and autism are not supported by the scientific evidence. But vaccines, like every other medical intervention we have, do carry with them some adverse risks. But the risks of not being vaccinated are far greater than the rare risk of serious complications for the vaccine."

Halsey reports receiving research funds from Merck for HPV vaccine research and serving on safety review committees for Novartis and Merck. He has conducted vaccine safety studies for the CDC.